On removable cycles through every edge

Mader and Jackson independently proved that every 2‐connected simple graph G with minimum degree at least four has a removable cycle, that is, a cycle C such that G/E(C) is 2‐connected. This paper considers the problem of determining when every edge of a 2‐connected graph G, simple or not, can be guaranteed to lie in some removable cycle. The main result establishes that if every deletion of two edges from G remains 2‐connected, then, not only is every edge in a removable cycle but, for every two edges, there are edge‐disjoint removable cycles such that each contains one of the distinguished edges. © 2002 Wiley Periodicals, Inc. J Graph Theory 42: 155–164, 2003     

Matroids with few non-common bases

In [On Mills's conjecture on matroids with many common bases, Discrete Math. 240 (2001) 271-276], Lemos proved a conjecture of Mills [On matroids with many common bases, Discrete Math. 203 (1999) 195-205]: for two (k+1)-connected matroids whose symmetric difference between their collections of bases has size at most k, there is a matroid that is obtained from one of these matroids by relaxing n₁ circuit-hyperplanes and from the other by relaxing n₂ circuit-hyperplanes, where n₁ and n₂ are non-negative integers such that n₁+n₂≤k. In [Matroids with many common bases, Discrete Math. 270 (2003) 193-205], Lemos proved a similar result, where the hypothesis of the matroids being k-connected is replaced by the weaker hypothesis of being vertically k-connected. In this paper, we extend these results.     

Preparation of composite materials containing iron in a cross-linked resin host based on styrene and divinylbenzene

Iron composite materials based on styrene/divinylbenzene network hosts were produced using aqueous suspension polymerization. The effects of different kinds of porogen agent, toluene, toluene/n-heptane mixture or a toluene solution of polyphenyleneoxide on the bulk density, swelling in toluene and ferromagnetic properties of these materials were evaluated. The specific area and average porous diameter of network resins were characterized by BET and BJH methods, while the iron content was determined by atomic absorption spectrometry. The morphology of the composites was studied by both optical microscopy and scanning electron microscopy with energy dispersive X-ray analysis. All the spherical beads, irrespective of their sizes, have agglomerated iron particles located only on their surface. The particles have exhibited ferromagnetic behavior, with a coercivity of 328.69 Oe. The porogen agents used affect the iron particle distribution on the bead surfaces.     

Tucumã (Astrocaryum vulgare) fat: an Amazonian material as a pharmaceutical input for lipid nanoparticle production

Journal of Thermal Analysis and Calorimetry - Native Amazon palm trees have been target of research and product development especially because of their oil and fat. Tucumã-do-Pará...     

Kinetic study of crystallization of PHB in presence of hydroxy acids

Poly(3-hydroxybutyrate), PHB, has been structurally modified through reaction with hydroxy acids (HA) such as tartaric acid (TA) and malic acid (MA). The crystallization kinetic of the samples was evaluated by isoconversional method through nonlinear fitting to obtain the estimation for activation energy (E _a ) and pre-exponential (A) values. The thermal behavior of the crystallization temperature, 44.8 and 58.9 °C at 5 °C/min, and results obtained to the average activation energy, 73 ± 9 kJ mol⁻¹ and 63 ± 1 kJ mol⁻¹, to PHB/MA and PHB, respectively, are suggesting that malic acid may be deriving plasticizer units from its own PHB chain. PHB/TA show increase in the medium value of E _a, 119 ± 2 kJ mol⁻¹ and T _c = 48.2 °C (at 5 °C/min), indicating that tartaric acid is probably interacts in different way to the of PHB chain (E _a=73 ± 9 kJ mol⁻¹, T _c = 44.8 °C at 5 °C/min).     

Dirac’s Theorem on Simplicial Matroids

We introduce the notion of k-hyperclique complexes, i.e., the largest simplicial complexes on the set [n] with a fixed k-skeleton. These simplicial complexes are a higher-dimensional analogue of clique (or flag) complexes (case k = 2) and they are a rich new class of simplicial complexes. We show that Dirac’s theorem on chordal graphs has a higher-dimensional analogue in which graphs and clique complexes get replaced, respectively, by simplicial matroids and k-hyperclique complexes. We prove also a higher-dimensional analogue of Stanley’s reformulation of Dirac’s theorem on chordal graphs.      

A reducing of a chaotic movement to a periodic orbit,of a micro-electro-mechanical system,by using an optimal linear control design

This paper analyzes the non-linear dynamics, with a chaotic behavior of a particular micro-electro-mechanical system. We used a technique of the optimal linear control for reducing the irregular (chaotic) oscillatory movement of the non-linear systems to a periodic orbit. We use the mathematical model of a (MEMS) proposed by Luo and Wang.     

Elements belonging to triangles in 3-connected matroids

An element e of a 3-connected matroid M is said to be superfluous provided M/e is 3-connected. In this paper, we show that a 3-connected matroid M with exactly k superfluous elements has at least

     

Total assignment of 1H and 13C NMR spectra of the alkaloid 3,3-diisopentenyl-N-methyl-2,4-quinoldione and novel reaction derivatives

One- and two-dimensional NMR experiments were used for the unambiguous assignment of the 1H and 13C NMR chemical shifts of 3,3-diisopentenyl-N-methyl-2,4-quinoldione and five novel reaction derivatives.